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Abstract

The aim of this controlled animal study was to
investigate the effect of low-level laser therapy (LLLT)
administered 30 min after injury to the Achilles tendon. The
study animals comprised 16 Sprague Dawley male rats
divided in two groups. The right Achilles tendons were
injured by blunt trauma using a mini guillotine, and were
treated with LLLT or placebo LLLT 30 min later. The injury
and LLLT procedures were then repeated 15 hours later on
the same tendon. One group received active LLLT (1=
904 nm, 60 mW mean output power, 0.158 W/cm2 for 50 s,
energy 3 J) and the other group received placebo LLLT 23
hours after LLLT. Ultrasonographic images were taken to
measure the thickness of the right and left Achilles tendons.
Animals were then killed, and all Achilles tendons were
tested for ultimate tensile strength (UTS). All analyses were
performed by blinded observers. There was a significant
increase in tendon thickness in the active LLLT group when
compared with the placebo group (p<0.05) and there were
no significant differences between the placebo and uninjured
left tendons. There were no significant differences in
UTS between laser-treated, placebo-treated and uninjured
tendons. Laser irradiation of the Achilles tendon at
0.158 W/cm2 for 50 s (3 J) administered within the first
30 min after blunt trauma, and repeated after 15 h, appears
to lead to edema of the tendon measured 23 hours after
LLLT. The guillotine blunt trauma model seems suitable for
inflicting tendon injury and measuring the effects of
treatment on edema by ultrasonography and UTS. More
studies are needed to further refine this model.